The field of the present invention is clutches in multiple clutch arrangements.
In certain vehicle uses, centrifugal clutches used for starting have been found advantageous. In certain such devices it has also been found advantageous to provide a manually actuated clutch for disengaging the drive train for changing gears and the like. One such clutch system has been devised and is illustrated in FIG. 1.
In FIG. 1, a clutch system 1 is shown positioned within the drive train of a vehicle between the variable speed engine output shaft 2 and a driven shaft 3. A starting clutch 4 of a centrifugal type is installed on the output shaft 2 to sense engine speed for engaging the clutch. Installed on the driven shaft 3 is a manually actuated clutch 5 of the multidisc type. The clutches 4 and 5 are coupled together in series. In such a system, when the number of revolutions of the engine is lower than a preselected value, the centrifugal clutch 4 is disengaged and power is not transmitted. When the speed of the engine increases, the centrifugal clutch 4 is engaged and the power transmission is then controlled manually by a clutch linkage 7 operating against spring mechanisms 6 exerting fixed clamping forces on the manually controlled clutch 5.
A difficulty encountered with arrangements such as shown in FIG. 1 is the shear size of the clutching mechanism. Because the two clutches 4 and 5 are arranged on different shafts, a large amount of space is required. In the example of FIG. 1, it is seen that the clutches may be placed in an overlapping manner. However, the arrangement can still be a problem for smaller vehicles having limited room.
Another difficulty encountered with clutches in general is that the clamping force of the spring mechanism 6 to prevent clutch slippage under anticipated power may be greater than desired for easy manual operation. Ironically, the heavy spring compression is typically not required under conditions when the clutch is to be actuated. When a manual clutch is employed, power is usually reduced and a full torque load is not experienced. When full power is directed to the drive train, a clutching operation is normally not undertaken.
When clutches having different functions are employed in series such as in the device of FIG. 1, the maximum torque to be transmitted through each clutch is the same. Consequently, each clutch is required to be equally strong, large enough to accommodate the transmitted torque and, necessarily, more expensive than might otherwise be required.